Weed Management in Horticultural Crops

CURATIVE METHODS

i) Eradication: Eradication means elimination of weeds after they have become established in an area and control methods are adopted where prevention and eradication have failed, so control measure as a rule eradicate the weeds and make it possible to raise the crops in spite of their presence. Constant control measures applied for several years help in practical elimination of weeds. Eradication is however, impractical and if practiced in large scale it may be possible to eradicate certain weeds which are limiting in their spread.

II) Methods of weed control: Methods of weed control can be decided by the habits of weed which concern with life cycle and methods of propagation by the habitat which mean magnitude of the problem

Habit- Concern its life cycle and methods of propagation
Habitat- Means place where it thrives best
Distribution- Means the magnitude of the problem

A. Physical/Mechanical methods of weed control

a) Prevention from spread
b) Destruction of top growth
c) Destruction of underground part
d) Destruction of weed seeds in the soil

a) Preventing from spread:

Use of clean seed: Certified and pure seeds should be used for the sowing purpose. Most of the seeds are full of impurities which help in the spread of weeds year after year. There should be a rule to stop the sale of uncertified seeds.

Prevention of seed production in weed contaminated and nearby waste areas: Weeds growing in waste lands, along roadside, fences, ditches etc produce seeds which are carried to adjoining areas of cultivated fields. Such areas should be properly controlled to prevent the formation of weed seeds.

b) Destruction of weed growth:

Hand pulling: Efficient method of weed control. Effective in destruction of weeds growing within the rows. This method should be adopted before seed formation takes place.

Hand hoeing: Old practice. Eliminates weeds from rows and help in stirring up of soil for soil aeration. Labour consuming process. Shallow rooted weeds are easily eliminated.

Tillage: Practical, oldest and widely practised method. If timely practised, it prevents the seed production. It is effective in perennial weeds. It is followed for crops grown in lines. Frequent tillage destroys the soil structure and thus is less favourable for growth. It is important in seed bed preparation of field crops but restricted in orchards.

Blind tillage: It means tillage of the soil after seeding the crop, either before the crop plants are up or while they are in the early stages of growth. Used in most of the crops and cereals. Various types of harrows are used in field even though seedlings of crop plants are not above the ground and repeated until plants are well advanced. This process results in increasing the grain yields.

Ploughing: It helps in burying of annual, biennial and perennial weeds. Ploughing is practiced before the seeding of crops and top growth of the weeds is checked by it. Deep ploughing in summer is effective in exposing the roots to the sun rays and killing them.

Mowing: Means removing the top growth of weeds growing in lawn/roadside and exhausting them to death. Repeated mowing prevents seed production and also starve the underground parts. It may require 1-3 years to control tall and perennial weeds by repeated and frequent cutting. Best time is when the underground root reserves are at the lowest level. Mowing removes apical dominance and repeated cutting hastens food depletion and death of the plant. Effective in tall growing plants. It favours short growing weeds plants by removing competition.

Harrowing: Successful in removal and destruction of small weeds. Adopted, where the surface of the soil is quite smooth, dry and free from obstruction. Objective is to loosen or cut the root system enough so that plant dies from desiccation (water losses) before it can re-establish its roots.

Disking: Adopted successfully in destroying the weeds by cutting and burring them in the soil after the crops are harvested.

Spudding: Spud is a tool with a long chisel like blade designed especially for the removal of weeds from the lawns without disturbing the soil.

Burning: Noxious weeds like dodder (Cuscutta) are destroyed by burning. It destroys the useful vegetation also and affects the soil.

Pasturing and grazing: Continued grazing of the tops of the weeds by animals prevents seed formation and ultimately exhausts the underground parts. Grazing should be allowed in a controlled manner to allow grazing on a limited area so that all weeds are grazed and not the tasty ones.

c) Destruction of underground parts:

Hand digging: Removal of underground parts like roots and rhizomes by hand digging, but it is an expensive method. Applied in small patches where noxious weeds have been found to grow.

Summer fallow: Continuous clearing of the land throughout summer without growing a crop. Effective if top growth of the weeds is removed at regular intervals to starve the roots. Fields may be ploughed, or disked. Employed in dry farming areas where crop depends on monsoon. It helps in the absorption of precipitation by the soil and in the retention of absorbed moisture.

d) Destruction of weed seeds in the soil:

Some of the weed seeds remain buried in the soil for years without losing their viability and come up and produce new crops. Steps should be taken to destroy the weeds and to clean the fields.

Deep ploughing: weed seeds which are buried below are exposed to the surface if deep ploughing is practised during summers. Such weed seeds are induced to germinate and once they come up, it is easy to control them.

Harrowing and shallow cultivation: These methods induce many seeds to germinate and can be destroyed during the preparation of seed beds.